* fix: OAuth tokens secure storage for Windows & Linux
* fix(mcp): MCP Tool Re-exposure & Strict Input Validation
Fixes the MCP re-exposure bug by correctly handling tool deduplication, input validation with Ajv, and structured output (including images). Also disables experimental API betas by default to prevent 500 errors on external accounts.
* fix(mcp): skip official registry prefetch in non-first-party mode
Prevents unnecessary calls to Anthropic's MCP registry when using other API providers.
* fix(cli): disable experimental API betas by default
This prevents 500 errors from Anthropic's API when tool-calling with non-Anthropic accounts or models that don't support certain beta features.
* fix: issues raised in the PR review for #675
